TOKYO — Japan pushed ahead Monday with its proposal for U.N. sanctions against North Korea for its missile tests, and China dispatched diplomats to Pyongyang amid a campaign to lure the reclusive regime back to nuclear disarmament talks.

The U.S. nuclear envoy Christopher Hill huddled with the Japanese foreign minister, Taro Aso, and other officials in Tokyo on the final stop of a tour of the region to coordinate a common strategy on last week's missile tests and urge Pyongyang to drop a boycott of six-party negotiations.

North Korea's missile tests last week caused no injuries or damage, but they sparked international condemnation. Officials in Japan - badly shaken by the tests - said Monday that they were mulling whether their constitution allowed preemptive strikes on North Korean missile targets.

The United States and countries in the region, however, were undecided on a U.N. response to the missile launches: Washington and Tokyo back sanctions, while Beijing and Moscow favor dialogue with the North.

Despite the opposition, Japan showed no signs of backing away from the U.N. resolution, which would prohibit nations from procuring missiles or missile-related "items, materials goods and technology" from North Korea. A vote at the U.N. could come later Monday.

"It's important for the international community to express a strong will in response to the North Korean missile launches," the Japanese chief cabinet secretary, Shinzo Abe, told reporters. "This resolution is an effective way of expressing that."

China was also active. Foreign Minister Li Zhaoxing "exchanged views" by phone on Sunday with his counterparts from 11 council members and South Korea, the Foreign Ministry said on its Web site. He "stressed that any action should be conducive to maintaining the peace and stability in the region and the unity of the Security Council," the two-sentence statement said without elaborating.

The Chinese visit came as the United States urged Beijing to use its considerable influence in North Korea to persuade the reclusive country to abandon further missile tests and return to six-party talks on its nuclear weapons programs.

The North has been boycotting the talks - which include South Korea, the United States, China, Japan and Russia - for months in protest of a U.S. crackdown on alleged North Korean counterfeiting, money-laundering and other financial crimes.

"China now has an opportunity to put its best foot forward, to send the North Koreans a direct message that these missile tests cannot be tolerated," Undersecretary of State Nicholas Burns said in Washington.

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The U.S. assistant secretary of state, Christopher Hill, met with Aso on Monday in Tokyo, where the American arrived after stops in Beijing and Seoul. Throughout the tour, Hill has emphasized the need for countries involved to present a united front.

"What North Koreans need to do is come to the next session of the six- party talks," Hill told reporters in between meetings in Tokyo.

Those talks came amid a widening split between Japan and South Korea on how to best approach the North. Seoul on Sunday issued a harsh rebuke on Japan's outspoken criticism of the North Korean tests.

"There is no reason to fuss over this from the break of dawn like Japan, but every reason to do the opposite," a statement from President Roh Moo-hyun's office said, suggesting that Tokyo was contributing to tensions on the Korean Peninsula.

The Japanese response on Monday to that was muted, saying only that it regretted the statement.

North Korea agreed in September 2005 to give up its nuclear ambitions in return for aid and energy, but no progress has been made to implement that accord.

As a way out of the impasse, China has suggested an informal gathering which could allow Pyongyang to technically stand by its boycott, but at the same time meet with the other five parties. Hill backed the proposal on Saturday and said Washington could meet with the North on the sidelines of such a meeting.

Japanese government officials on Monday openly discussed whether the country ought to set up the legal framework to allow Tokyo to launch a preemptive strike against Northern missile sites.

"If we accept that there is no other option to prevent an attack ... there is the view that attacking the launch base of the guided missiles is within the constitutional right of self-defense. We need to deepen discussion," Abe said.

Japan's U.S.-drafted constitution, untouched since it was enacted after World War II, foreswears the use of war to settle international disputes, and its provisions have severely limited the country's military.